This is a Shannon award providing partial support for the research projects that fall short of the assigned Institute's funding range but are in the margin of excellence. The Shannon award is intended to provide support to test the feasibility of the approach; develop further tests and refine research techniques; perform secondary analysis of available data sets; or conduct discrete projects that can demonstrate the PI's research capabilities or lend additional weight to an already meritorious application. The abstract below is taken from the original document submitted by the principal investigator. DESCRIPTION: Nucleotide excision repair (NER) is an important cellular defense mechanism against mutagenesis and carcinogenesis. Defects in this repair pathway also lead to complex human hereditary diseases such as xeroderma pigmentosum, Cockayne syndrome, and trichothiodystrophy. Thus, understanding the biochemical process of NER and identifying all of the components in the pathway will not only enable us to gain insights into a fundamental biological function, but also contribute to the understanding of human carcinogenesis, as well as human repair diseases. The objectives of this proposal are to define the biochemical pathway of NER in eucaryotes using the yeast Saccharomyces cerevisiae as a model system and to understand the regulatory aspects of the interaction between excision repair and transcription. These objectives will be achieved by identifying proteins required in DNA damage recognition, incision, excision, DNA repair synthesis, and DNA ligation. The roles of Rad7, Rad16, and Rad23 in NER will also be investigated. This proposal will utilize a combination of approaches including a yeast cell-free system for NER, protein and protein complex purification and characterization, functional assays, dissection of NER pathway into individual biochemical steps, and molecular cloning. When successfully carried out, these proposed studies should lead to the identification of all yeast proteins required in NER, thus, defining a complete biochemical pathway for the repair.